1. Field of the Invention
The present invention relates to a gate driving circuit and a display apparatus having the gate driving circuit. More particularly, the present invention relates to a gate driving circuit that may have improved reliability during high-temperature operations and a display apparatus having the gate driving circuit.
2. Discussion of the Background
In general, a liquid crystal display device includes a liquid crystal display panel having a lower substrate, an upper substrate facing the lower substrate, and a liquid crystal layer interposed between the lower substrate and the upper substrate in order to display an image.
The liquid crystal display panel includes a plurality of gate lines, a plurality of data lines, and a plurality of pixels connected to the gate lines and the data lines. A gate driving circuit, which provides a gate signal to gate lines, may be formed directly on the liquid crystal display panel through a thin film process.
Generally, a gate driving circuit may include a shift register in which multiple stages are connected to each other in series. Each stage includes a plurality of transistors to apply a gate voltage to a corresponding gate line of the gate lines. Specifically, each stage may include a pull-up transistor connected to a gate line to output a gate voltage and a carry transistor connected to an input terminal of the next stage to output a carry voltage that is used to control the driving of the next stage. Therefore, the gate driving circuit may prevent a distorted signal caused by a load connected to the gate line from being applied to the next stage, thereby preventing malfunction thereof.
The control terminals of the pull-up transistor and the carry transistor may be commonly connected to a Q-node in each stage. The Q-node has an electric potential of a turn-off voltage that is lower than a threshold voltage during a (n−1)H period where a gate voltage and a carry voltage are maintained at a low state. On the other hand, the Q-node has an electric potential of a turn-on voltage that is higher than the threshold voltage during a 1 H period (one horizontal scanning period) where the gate voltage and the carry voltage are maintained at a high state.
However, the electric potential of the Q-node may be floated during a predetermined period of the (n−1)H period. Thus, when the electric potential of the Q-node is not maintained at the turn-off voltage, the pull-up transistor and the carry transistor may be turned on, thereby causing a ripple of the gate voltage and the carry voltage. Particularly, when current characteristics of the pull-up transistor and the carry transistor are varied while testing a liquid crystal display panel under a high-temperature condition, a malfunction of the gate driving circuit may be caused by noise being applied through the floated Q-node, thereby deteriorating high-temperature reliability of the gate driving circuit.